Recovery of fibrous material from waste waters of the paper, cardboard and celluloseindustry by addition of condensation of urea and an alkyleneimine



United States Patent 3,399,110 RECOVERY OF FIBROUS MATERIAL FROM WASTE WATERS OF THE PAPER, CARDBOARD AND CELLULOSE INDUSTRY BY ADDITION OF CON- ice number of diflerent substances used for improving the flotation are highly sensitive to fluctuations of this kind.

Moreover, it is known that some of the products used for the flotation as foamers and fiocculants may cause DENSATION 0F UREA AND AN ALKYLENE 5 undesirable secondary phenomena during the processing [MINE of the recovered pulp, such, for example, as uneven trans- Hans'Sommer, Hofheim, Taunus, Herbert Bestian, Frankp y stalns m e p p formatwn caused y furt am Main, and Dieter Bergmann, Munchberg, Upper the attack of bacteria and sticking of the paper web to Franconia, Germany, assignors to Farbvverke Hoechst the press. Aktiengesellschaft vormals Merster Lucius & Brumng, NOW we h f d that the fl t ti propel-ties f 22: 3:? am i Germany a corporatlm of waste waters of the paper, cardboard and cellulose No Drawing. Filed Mar. 11, 1965, Ser. No. 439,092 Industry a be g f f f f; Claims priority, application Germany, Mar. 14, 1964, P Q Pro nets 0 tame y con ensatlfm y F 42,333 immes and urea. The process of the invention improves 2 Claims 31, 1 2 190 15 the speed of flotation as well as the clearing effect and,

in addition, constitutes an improvement from the economical point of view.

The nitrogenous products obtained by condensation of ABSTRACT OF THE DISCLOSURE urea and 1,2-alkylene-irnines carrying a substitutable hy- Fibrous material is recovered from waste waters in drogen atom at the nitrogen atom and/or their oligomers the paper, cardboard and cellulose industry, by adding to are largely insensible to different compositions of the the waste water a nitrogenous product obtained by conwaste water and do not cause any undesirable secondary densation of urea and an 1,2-alkylene imine or oligomer phenomena when the recovered fiber and filler portions thereof having a substitutable hydrogen atom at the nitroare processed again. gen atom, the nitrogenous product being added in an It is especially surprising that, in contradistinction to amount between 0.1 and 4% by weight of the solid and the experience made up to now, the addition of surfacesuspended particles. active substances is not required for the foam stabilization.

For carrying out the tests leading to the results specified in the table a waste water was used having a charge In order to improve the flotation, a tendency to creamof 1600 mg. of solid and suspended particles per liter ing-up is imparted to the solid and suspended particles at a pH-value of 5.8. In order to determine the time of Test Flotation Yield in exampl Additions of flotation time (in Clearing efiect evacuated No. auxiliary agents (in mg.) seconds) judged visually flotation cell (percent) Over 400 Turbid (deposit)-. 62.4 5 (comparative product con- 400 Turbid 61.2

taining animal glue). 3 10 (comparative product 400 do 62.1

containing animal glue). 4 5 (comparative product con- 360 do 64.6

taining castonoil). 5 10 (comparative product con- 360 do 65. 1

taining caster-oil). 6 5 condensation product 90 Almost clear 79. 0

from 1,2-a1kylene-imine and urea. 7 10 condensation product 38 Clear 84. 5

from 1,2-alkylene-imine and urea. 8 10 polyethylene imine 105 Slight deposit..." 75. 2

present in the waste water by addition of various chemicals. It is presumed that the nature of the flotation process resides in the reciprocal actions of accumulated electric charge and surface-active power potentials as well as in the stabilization of the separation between water and solid particles provoked by the corresponding chemicals. The paper pulp present in the waste water is brought to the surface of the vessel by flotation, enriched there and after thickening used again for the production of paper.

In order to improve the flotation there have been used up to now, for example, sulfonated fatty matters, products containing animal glue and wax soaps. Frequently, components having a flocculating action are added which in combination with soaps or other surface-active substances are intended to improve the flotation.

In order to render the flotation process a secure method of operation and to ensure an optimal fiber recovery rate, a flotation auxiliary agent applicable in practice should show a uniform action under different and changing conditions, such, as they are caused by fluctuations usually occurring in the composition of matter, the filler portion, the colloid content, the electrolyte content and the pH-value of the waste waters. As is known, a large flotation 800 cc. of this Waste water were introduced into a shaking cylinder and the flotation auxiliary agents were added. In each case, the whole was shaken under the same conditions, slightly evacuated and the flotation time measured in seconds.

According to the invention the products obtained by condensation of 1,2-alkylene-imines and urea are added to the aqueous suspension of the fibrous material in a quantity within the range from 0.1 to 4% referred to the solid and suspended particles.

The nitrogenous condensation products from 1,2- alkylene-imines and/or their oligomcrs and urea, which are water-soluble or self-emulsifying in water are obtained by reaction of the components. The reaction is usually carried out at a temperature within the range from about 40 to about 200 C. in the presence or in the absence of solvents or diluents, preferably in the presence of water. In order to accelerate the reaction acid catalysts may be used additionally. The advancing condensation of the products can be judged from the viscosity and the solubility of the condensation products in water.

As 1,2-alkylene-imines there may be used ethyleneimine, 1,2-propylene-imine, 1,2- or 2,3-butylene-imine or 3 2,2-dimethyl-ethylene-imine. Apart from the monomeric cyclic compounds there are also suitable the dimeric, trimeric and similar oligo-meric forms, preferably oligomers of ethylene-imine and of 1,2-pr0pylene-imine. The preparation of the oligomeric alkylene-imines is described in Houben-Weyl Methoden der organischen Chemie, 4th edition, vol. XI/2, page 261.

We claim: I

1. A process for improving the recovery of fibrous material from waste waters of the paper, cardboard and cellulose industry, which comprises adding to the waste water a nitrogenous product obtained by condensation of urea and a member selected from the group consisting of an 1,2-alkylene-imine, carrying a substitutable hydrogen atom at the nitrogen atom and oligomers thereof, wherein the nitrogenous product is used in an amount from 0.1 to 4% referred to the solid and suspended particles.

2. A process as claimed in claim 1, wherein a condensation product of 1 mol of urea and 1 mol of ethyleneimine is used as nitrogenous product.

References Cited UNITED. STATES. PATENTS 3,131,144 *4/1964 Nagan. 3,259,569 7/1966 Priesing 7210-54 X 3,345,253 10/1967 Bestian.

DONALL H. SYLVESTER, Primary Examiner.

15 H. R. CAINE, Assistant Examiner. 

